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Pale Cyst Nematode (PCN) Eradication Program - Idaho Falls, Idaho

2023 3rd Quarter Report (July 1st – September 30th) 

PROGRAM UPDATES AND NEW INFORMATION: 

• The current Pale Cyst Nematode (PCN) regulated area, which spans portions of northern Bingham 

and southern Bonneville Counties, is 6,535 acres (3,542 acres of infested fields and 2,993 acres of 

associated fields). The PCN infestation is limited to an area with an 8.5-mile radius and represents 

less than 1% of Idaho’s total potato production areas. 

ERADICATION ACTIVITIES

• The PCN program contracted with a licensed chemical applicator to fumigate seven PCN-infested 

fields (approximately 754 acres) with the nematicide Telone II® (1,3-dichloropropene). Fumigation 

was completed on the seven fields in October 2023. 

REGULATORY DATA

Table 1. Number of Pieces of Equipment Treated by PCN Program by Treatment Type

Treatment type 3rd Quarter 

of 2023 

2023 Year 

to Date 

Since Program 

Inception (2006) 

Pressure washed 643 1,073 34,733 

Steam Sanitized 104 178 5,657 

Total 747 1,251 40,390 

Table 2. Number of Pieces of Equipment Treated by Stakeholders Participating in the SelfCertification Program

Treatment type 2nd Quarter 

of 2023* 

2023 Year 

to Date* 

Since Program 

Inception (2006) 

Pressure washed 13 13 4,955 

*Self-certification data lags all other program data as stakeholders have three months after the end of each quarter to self-certify. 
 

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Table 3. Regulatory Documentation Issued by PCN Program

Documentation type 3rd Quarter 

of 2023 

2023 Year 

to Date 

Since Program 

Inception (2006) 

Active

Certificates (PPQ* 540) 243 443 15,568 ** 

Limited Permits (PPQ 530) 65 109 4,484 ** 

Compliance Agreements (PPQ 519) 2 15 ** 29 

*Plant Protection and Quarantine (PPQ); **Not applicable

SURVEY DATA

• To date, the PCN program has collected 543,795 soil samples in Idaho outside of the 32 known 

infested fields. 

Table 4. Soil Samples Collected in Idaho

Type of Survey 3rd

Quarter of 

2023 

2023 Year 

to Date 

Since Program 

Inception (2006) 

Detection 8 246 246,494 

Delimiting 136 637 297,301 

Eradication 634 830 200,557 

Total 778 1,713 744,352 

LABORATORY DATA

• Since 2009, the PCN program has collected and screened 89,379 soil samples in support of the Idaho 

State Department of Agriculture’s (ISDA) post-regulation monitoring survey of fields deregulated 

by the Animal and Plant Health Inspection Service (APHIS). Note: this data stays static, because the 

ISDA no longer conducts post-regulation monitoring surveys. 

• Since program inception, the PCN laboratory has screened 107,496 soil samples collected in other 

potato-producing states. There have been no PCN detections in the United States outside of Idaho. 
 

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Table 5. Samples Processed by the PPQ Idaho Falls PCN Laboratory

Type of Survey 3rd Quarter 

of 2023 

2023 Year 

to Date 

Since Program 

Inception (2006) 

Detection 292 7,189 296,326 

Delimiting 501 501 288,551 

Eradication 12 684 199,346 

Total 805 8,374 784,223 

Table 6. Historic Info: Samples Processed at Other Idaho Laboratories

Type of Survey Idaho Food Quality Assurance 

Laboratory (2006-2009, now closed) 

Idaho State Parma Research and 

Extension Center (2006-2009) 

Detection 52,670 69 

Delimiting 10,227 896 

Total 62,897 965 

ERADICATION MONITORING AND PROGRESS

• Since its inception in 2006, the PCN program has used a staining technique to analyze the viability 

of nematode eggs in 1,059 cyst samples. The cyst samples are composited from subsamples of cysts 

collected from infested field-monitoring grids before and after fumigation treatments. Viable 

nematode eggs have not been detected in 24 of the 32 infested fields, which advances those 24 fields 

to the next phase of evaluating eradication progress, the greenhouse bioassay. 

Table 7. Viability Cyst Stain Results Summary as of September 30, 2023 

Location Total number of 

infested fields

Total number of infested fields with 

no viable PCN detected by stain

Idaho Falls PCN Laboratory 32 24* 

*One Infested Field in Bingham County has proceeded to Infield Greenhouse-Bioassay since no cysts have been collected in following 

surveys. 

• Greenhouse bioassay is a test of the nematode’s ability to hatch, feed, and reproduce when cysts are

placed in proximity to a growing host plant. Currently 22 of the 24 fields have successfully 

completed the greenhouse bioassay test. Of the two remaining fields currently in greenhouse 

bioassay testing, results are expected in spring 2024. 
 

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• The PCN program continues to monitor and regulate fields after successful completion of 

greenhouse bioassay testing, but with reduced sanitation requirements. Fields that have passed the 

greenhouse bioassay test are also eligible to return to potato production at the landowners’ 

discretion.

Table 8. Greenhouse Bioassay Results Summary as of September 30, 2023

Greenhouse bioassay 

location 

Fields that advanced to 

greenhouse bioassay testing

Fields that passed 

greenhouse bioassay testing

University of Idaho, Moscow 23 22 

Bingham County 1 0 

Total 24 22 

• The PCN program requires infested fields that return to potato production to undergo full-field 

surveys following each of three subsequent potato crops to check for viable PCN populations.

• Between 2015 and 2022, potatoes were planted on eleven eligible fields, which were the first potato 

crops grown since PCN was first found on those fields. 

• Viable nematodes were found in soil samples collected from five of these fields following potato 

harvest. As a result of finding viable nematodes on these five fields, the program reinstated 

prohibitions on growing potatoes, and full sanitation treatments for equipment and vehicles leaving 

the fields (pressure washing and steam treatment). 

• No viable nematodes were found in soil samples from the other six fields, making them eligible to 

grow another potato crop, which is at the landowners’ discretion. Of these six fields, five have 

successfully completed one round of in-field bioassay, and one field has successfully completed two 

rounds of in-field bioassay. 

Table 9. In-field Bioassay Results Summary as of September 30, 2022 

Fields that have passed one

round of in-field bioassay 

(viable nematode eggs not

detected following harvest)

Fields that have passed two

rounds of in-field bioassay 

(viable nematode eggs not

detected following harvest)

Fields that did not pass in-field 

bioassay (viable nematode 

eggs were detected following 

harvest)

5 1 6* 

*Viable nematodes detected after one crop on four fields, and after two crops on two field.
 

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Table 10: Eradication Progress Summary as of September 30, 2023

 

*No cysts have been detected since 2015 in a Bingham County field (149.6 ac) following the litchi tomato trap crop. In the spring of 

CY2023 potatoes were planted only in the monitoring grids for the first round GH bioassay test. The rest of the field was planted to wheat.

IMPACTS ON COMMERCE

In response to the initial PCN detection in 2006, Canada, Mexico and Korea shut off importation of 

potatoes from Idaho, while Japan cut off importation of potatoes from the entire United States. The 

Mexico and Canada export markets have both been re-opened except for potatoes from PCN-regulated 

areas. Both require PCN soil surveys from origin fields. The Korea market was reopened in June 2010 

except for potatoes originating from Bingham and Bonneville Counties, Idaho. Japan reopened the 

market for all except Idaho potatoes in February 2007 and to Idaho potatoes in September 2017. This 

action represented a major milestone for the Idaho potato industry and the PCN program, the full 

restoration of all markets lost due to the original 2006 PCN detection. Because of extensive field surveys 

conducted throughout production areas in Idaho, all of which have been negative beyond the twentynine infested fields, the general opinion by trading partners is that potatoes produced outside regulated 

areas do not pose a risk for spread of PCN.

PUBLIC OUTREACH

Pale Cyst Nematode program information is available via the USDA APHIS Stakeholder Registry. The 

Registry allows anyone to subscribe and receive alerts by email or by text message when new 

information about PCN or other topics of interest are announced. Subscribing is simple and you can 

unsubscribe or change your selections at any time. For PCN program announcements, select Plant 

Health in the U.S. (Domestic), then Pest Management, and finally Potato Pests and Diseases. To sign up, 

visit https://public.govdelivery.com/accounts/USDAAPHIS/subscriber/new

More PCN program information can be found at:

https://www.aphis.usda.gov/aphis/ourfocus/planthealth/plant-pest-and-disease-programs/pests-anddiseases/nematode/pcn

If you have additional questions, contact the PCN program office at (208) 522-2431, 

Monday through Friday, 8:00 AM to 4:30 PM (Mountain Time), excluding federal holidays. 

Field Status

Number 

of 

Fields

Acres

Passed Greenhouse Bioassay Test: Eligible to Return to Potatoes and 

start the In-Field Bioassay Test (See Table 9 for in-field bioassay 

results summary)

22 2,485.8

Passed Viability Test: Greenhouse Bioassay Test in Progress 2* 225.9

Viable PCN: One or more Telone treatments 7 754.4

Viable PCN: No Treatment to Date 1 76.8

Total 32 3542.9